US3794424A - Method and apparatus for determining the color or cut diamonds - Google Patents

Method and apparatus for determining the color or cut diamonds Download PDF

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Publication number
US3794424A
US3794424A US00121111A US3794424DA US3794424A US 3794424 A US3794424 A US 3794424A US 00121111 A US00121111 A US 00121111A US 3794424D A US3794424D A US 3794424DA US 3794424 A US3794424 A US 3794424A
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Prior art keywords
diamond
light
cut
optical transmitter
light conductor
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Expired - Lifetime
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US00121111A
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English (en)
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M Eickhorst
G Lenzen
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Individual
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Individual
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Priority claimed from DE19702011931 external-priority patent/DE2011931C2/de
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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/389Precious stones; Pearls
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01JMEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/46Measurement of colour; Colour measuring devices, e.g. colorimeters
    • G01J3/50Measurement of colour; Colour measuring devices, e.g. colorimeters using electric radiation detectors
    • G01J3/51Measurement of colour; Colour measuring devices, e.g. colorimeters using electric radiation detectors using colour filters
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/84Systems specially adapted for particular applications
    • G01N21/87Investigating jewels
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01JMEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/46Measurement of colour; Colour measuring devices, e.g. colorimeters
    • G01J3/50Measurement of colour; Colour measuring devices, e.g. colorimeters using electric radiation detectors
    • G01J3/501Colorimeters using spectrally-selective light sources, e.g. LEDs

Definitions

  • the determination method with the aid of the Ulbricht-spere is incorrect, in so far as the surface reflections of the light rays entering the diamond are included in the consideration, i.e., they are included in the measured value.
  • lt is a fact, well known to those skilled in the art, that the color of a diamond depends on structural inhomogeneities i.e., that the light entering the diamond and being reflected therein is subjected to an absorption which is the cause of the color. However, if this absorption is to be measured, and the components of the surface reflection are not excluded, this will always lead to incorrect measurement results.
  • a light beam is used entering a preselected cut surface, preferably the upper planar surface.
  • the rays reflected by the facets are registered in a light sensitive layer after the selected cut surface has been adjusted by suitable means to occupy a defined, repeatable spatial position relative to the axis of the light beam, and the light sensitive layer occupies a defined position relative to the jewel.
  • This apparatus operates in accordance with the recognition that the light beams reflected within the jewel and emerging therefrom may be registered on a light sensitive layer, and that they result for each jewel, provided the jewel may always be brought into an exactly defined and repeatable position, in a specific pattern which practically represents an identification of the jewel and may be used to identify the same. This means that at another time and at another location a second diagram may be made, and by comparing the two diagrams it may be determined by registering the image points of the two diagrams whether the same jewel is involved.
  • the main object of this invention is to provide a method and an apparatus for determining the color of cut diamonds which is reproducible at any time particularly for comparison with the internationally known and commercially customary color scale of cut diamonds, wherein the drawbacks of the known methods and apparatii are avoided, wherein the technical expenditure is to be kept low, the possibility of adjustment is as simple as possible, and wherein particularly the subjective errors in operation are to be avoided.
  • Further objects of the invention include: 1. To provide a method for determining the color of cut diamonds cut according to any pattern by using a ray entering through the upper planar surface of the diamond and being reflected totally according to the geometric configuration of the rays within the diamond, wherein the amount of attenuation between the entering and emerging ray of light of a defined predetermined wave length is measured photoelectrically, whereby attenuations of the entering ray caused by surface reflections and by varying adjustments of the cut diamond are avoided.
  • the means generating the selective light rays consist of a light source and a rotating filter wheel disposed in front thereof the number of filters arranged on the filter wheel corresponding to the number of the desired wave length.
  • the light conductor for the entering rays, the holderfor the diamond, and the optical transmitter are forming a unit, wherein the engaging surface of the light conductor and entrance surface of the transmitter are disposed in an optical planar plane, which is contacted by the upper planar surface of the diamond preferable under the force of a spring, and wherein preferably the space formed between the surface of the holder and the optical planar plane is closed by a mirror.
  • the light conductor is at least partly arranged within the optical transmitter, the light conductor and the optical transmitter consisting preferably of flexible fibrous optics, or of light conducting rods surrounded by an encasement.
  • the photoelectric receiver is a variably controllable element with respect to its sensitivity, or its amplification respectively.
  • the electronic circuit comprises a demodulator controlled by the filter wheel and splitting the output signals of the photoelectric receiver, channels receiving the split signals, matching means as signed to one of the channels, and regulating means arranged in an additional channel and connected to setting means and fed back to the photoelectric receiver, wherein the channels are coupled by the indicator of the measured value.
  • each diamond has a defined constant light absorption, due to the structural inhomogeneities depending on the wave length, which is measured according to the invention.
  • the constant difference between the intensity of the entering ray of a defined wave length and the ray totally reflected within the diamond and emerging from the facets of the upper side are measured. This difference, which allows a direct determination of the color of the diamond, may be ascertained anew at any time, if it is assured, according to the prerequisite of the invention that losses or diffusion effects are avoided, and its intensity may be regarded as 100 percent.
  • the attenuation amount of the two predetermined wave lengths is determined allowing to calculate for each one thereof the transmission of the diamond and based on these transmissions of the two predetermined wave lengths a quotient may be formed, representing an absolute constant for each diamond, because by forming the quotient, errors appearing in equal extents when the transmissions for both wave lengths are determined are nullified, since the measurement takes place in one adjustment of the diamond, or the apparatus respectively.
  • errors are eliminated caused by subjective deficient operations, such as faulty positioning of the diamond in the holder of the apparatus, or adjustment deviations of the entering light, but also technical faults in the finish of the diamond, which may be caused by a geometrically inexact cut.
  • the second wave length represents a reference wave length.
  • a modified method of the invention provides to use monochromatic light of more than two wave lengths for measuring, one of which including the absorption maximum of the diamond at A 415,5 nm while the other one is within the range of the visible spectrum above 500 nm.
  • the quotient is formed of the value derived from the wave length for A 415,5 nm and of one of the two higher wave lengths, while the third measurement serves to obtain a correction factor.
  • the apparatus according to the invention shown in the drawing comprises a light conductor 1 for the entering rays, a holder 2 for a diamond 24 which, in this case, has the facet pattern of a brilliant, and an optical transmitter 5 construed to form a unit having, particularly the optical transmitter 5, a cylindrical shape including an outer corresponding cover 6.
  • the light conductor 1 and the optical transmitter 5 are arranged in such a manner that their surfaces facing the diamond are disposed in an optical planar plane 4.
  • the space formed between the surface of the holder 2 and the optical planar plane 4 is closed by a mirror 3.
  • any suitable means such as a spring. It is important that the upper planar surface of the cut diamond, in this case a brilliant, contacts the plane 4 in an optical unique manner in order to avoid reflections or other diffusions.
  • the holder 2 for the diamond 24 is constructed in such a manner that the diamond is supported below its holder or mounting edge, while the upper portion of the diamond, that is the portion disposed above the mounting edge, is fully exposed so that all of the light is reflected according to the geometric configuration of the rays within the cut diamond and freely emerges out of the upper portion and gets into the optical transmitter 5.
  • the holder 2 includes a receiving cone cut in accordance with the cut pattern of the underside of the diamond 24, whereby the diamond may be inserted without any difficulties and the holder may be used for diamonds of different sizes all having the same cut pattern, i.e., for greater and smaller brilliants since, as is well known, the apex angle of the lower portion is always equal in case of brilliants.
  • the apex angle of the lower portion is always equal in case of brilliants.
  • the light conductor 1 as well as the optical transmitter 5 may be formed by a flexible fibrous optic, or also by a light conducting rod fed by means generating light consisting substantially of a source of light 23 and a filter wheel 8 arranged between the source of light and the light conductor 1, while therebetween an imageforming optic 9 is arranged in a known manner.
  • the filter wheel 8 has two filters '71, 72 arranged thereon each only allowing the passage of light of a desired wave length.
  • the light conductor 1 and thus also the diamond only receives light of two wave lengths.
  • more than two filters may be provided, whereby it is possible to generate monochromatic light of more than two wave lengths.
  • the one filter 71 is provided for light corresponding to the wave length A, 415,5 nm representing the maximum absorption of diamonds, while the other filter 72 allows the passage of light with a wave length of A 520 nm.
  • a further imageforming optic 10 is arranged bundling the light and projecting it upon a photoelectric receiver 11, which may be a photo resistance or, as in the present case, a photo multiplier in form of a secondary electronic multiplier.
  • the sensitivity, or amplification respectively, of this photoelectric receiver 11 is variably controllable.
  • the photoelectric receiver 11 is connected to a demodulator 12 from which two channels l8, l9 emerge conducting the signals split by the demodulator 12, which for synchronized control is connected to the filter wheel 8.
  • the two channels l8, 19 are coupled tQ each other by an indicator 16 for the measured value and the channel 19 includes matching means 15, while in channel 18 regulating means 14 including setting means 13 are provided.
  • the regulating means 14 is fed back to the photoelectric receiver 11.
  • the apparatus is standardized, or matched respectively, by placing, instead of a diamond 24, a mirror under 45 below the planar plane 4.
  • Light of the source of light 23 bundled by the image-forming optic impinges upon the two filters 71 and 72 of the rotating filter wheel 8, and each of the filters allows only the passage of light of a defined wave length.
  • the light passing the light conductor 1 impinges upon the mirror and is reflected to impinge via the optical transmitter 5 and the second image-forming optic 10 upon the photoelectric receiver 11 which trasforms it into an electrical transmission signal 22 fed to the demodulator 12 which demodulates the signals 22 derived from the filter wheel 8 and synchronized by the connection 21 and separates and feeds them to the associated channel 18, or 19 respectively.
  • the matching of a signal regarding its level takes place which is fed from the setting means 13 to the regulator 14, while the feed-back 17 takes care that the sensitivity of the photoelectric receiver 11 is adjusted so that the signal in channel 18 has the same level as the signal in channel l9.
  • the gauging of the apparatus is accomplished if the value appearing at the indicator of the measured value equals 1, Le, when the two intensities of the two used wave lengths are equal, and thus the quotient thereof is l.
  • the cut diamond is placed in the holder 2 and urged in tight contacting engagement against the optical planar plane 4. Now the path of rays is evidently the same as during the gauging process. However, due to the structure of the diamond and the two wave lengths being used, two different signals are received in the channels 18 and 19.
  • the signal in channel 18 is compared with the signal of the setting means 13, and, if necessary, is readjusted by means of the feed-back 17. Since the sensitivity of the photoelectric receiver 11 is altered by this feed-back 17, the signal in channel 19 will be altered the same amount. The change of this amount appears at the indicator 16 of the measured value and corresponds to the quotient of the two measured transmissions. This quotient represents a constant of the measured diamond, which may be measured anew, at any time, and anywhere.
  • the contacting surface of the optical transmitter 5 is always greater than the diameter of the upper planar surface of the diamond to be measured, while the exit cross sectional area of the light conductor 1 should be smaller, or at the utmost equal to the diameter of the upper planar surface.
  • any homogeneous, light-transmissive material may be used for the optical transmitter 5, and also a cylinder with inwardly arranged mirrors may be used.
  • the photoelectric receiver may be arranged directly on the optical transmitter 5, whereby the construction of the apparatus may still be simplified, since practically the image-forming optic 10 is eliminated.
  • An apparatus for determining the color of cut diamonds of any cut pattern comprising in combination and in functional series arrangement means for generating selective light beams of at least two defined wave lengths,
  • an optical transmitter receiving the rays which are totally reflected within the diamond
  • the light conductor and the optical transmitter consist of least two defined wave lengths, said means being in the form of a rotatable filter wheel, said demodulator splitting the output signals of the photoelectric receiver, two channels receiving the split signals, adjustable resistance means in one of the two channels, and a regulator in the other of the two channels, a set-point adjustment, said regulator being connected to said setpoint adjustment and back-coupled to said photoelectric receiver, whereby the two channels are coupled to the register for the measured values.
  • a method for determining the color of cut diamonds of any out pattern, especially the pattern of a brilliant cut comprising the steps of projecting beams of at least two defined predetermined wave lengths of monochromatic light one after the other into the planar upper surface of the diamond being examined, and measuring photoelectrically the amount of attenuation of two reflected beams emerging from the facets of the upper side of the diamond parallel to and in opposite direction to the projected beams.

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  • Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • General Health & Medical Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Engineering & Computer Science (AREA)
  • Food Science & Technology (AREA)
  • Medicinal Chemistry (AREA)
  • Investigating Materials By The Use Of Optical Means Adapted For Particular Applications (AREA)
  • Spectrometry And Color Measurement (AREA)
US00121111A 1970-03-13 1971-03-04 Method and apparatus for determining the color or cut diamonds Expired - Lifetime US3794424A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE19702011931 DE2011931C2 (de) 1970-03-13 Vorrichtung zur Bestimmung der photometrischen Transmission geschliffener Diamanten

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US3794424A true US3794424A (en) 1974-02-26

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JP (1) JPS5423270B1 (xx)
GB (1) GB1316382A (xx)

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3867032A (en) * 1973-03-20 1975-02-18 Diharo Diamanten Handels Compa Arrangement for objectively evaluating characteristics of gems, particularly diamonds
EP0007809A1 (en) * 1978-07-28 1980-02-06 Gem Instruments Corporation Apparatus for producing a simulated visual image of a selected gemstone
US4259011A (en) * 1979-11-05 1981-03-31 Crumm John C Optical gem analyzer
US4291975A (en) * 1979-10-03 1981-09-29 Scientific Gem Identification, Inc. Apparatus for determining the color characteristics of a gem
US4384769A (en) * 1981-05-08 1983-05-24 Jos. Schneider Optische Werke Aktiengesellschaft Illuminating system for test projector
US4569594A (en) * 1982-10-14 1986-02-11 Nestec S.A. Color value measurement
DE19506192A1 (de) * 1995-02-23 1995-07-20 Christian Gassner Edelstein-Absorbtionsspektralphotometer
US5835205A (en) * 1996-02-12 1998-11-10 C3, Inc. Optical testing system for distinguishing a silicon carbide gemstone from a diamond
US5835200A (en) * 1990-04-24 1998-11-10 Gersan Establishment Method and apparatus for examining an object
US6473164B1 (en) 2000-02-16 2002-10-29 Gemological Institute Of America, Inc. Systems, apparatuses and methods for diamond color measurement and analysis
US20060190292A1 (en) * 2000-10-12 2006-08-24 Gemological Institute Of America, Inc. Systems and methods for evaluating the appearance of a gemstone
WO2007069242A1 (en) * 2005-12-12 2007-06-21 Platform Development & Investment Ltd. Assessment of diamond color
US20080140961A1 (en) * 2006-12-07 2008-06-12 Atherton William E Single channel memory mirror
USRE44963E1 (en) * 1997-01-10 2014-06-24 Diamond Technologies, Inc. System and method for computerized evaluation of gemstones

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1744485A (en) * 1925-02-21 1930-01-21 Gustave L Herz Method and means for the examination of jewels
US2960909A (en) * 1957-01-07 1960-11-22 Jr Robert M Shipley Method for determination of color of gems
US3418053A (en) * 1964-08-28 1968-12-24 Technicon Instr Colorimeter flow cell

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1744485A (en) * 1925-02-21 1930-01-21 Gustave L Herz Method and means for the examination of jewels
US2960909A (en) * 1957-01-07 1960-11-22 Jr Robert M Shipley Method for determination of color of gems
US3418053A (en) * 1964-08-28 1968-12-24 Technicon Instr Colorimeter flow cell

Cited By (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3867032A (en) * 1973-03-20 1975-02-18 Diharo Diamanten Handels Compa Arrangement for objectively evaluating characteristics of gems, particularly diamonds
EP0007809A1 (en) * 1978-07-28 1980-02-06 Gem Instruments Corporation Apparatus for producing a simulated visual image of a selected gemstone
US4291975A (en) * 1979-10-03 1981-09-29 Scientific Gem Identification, Inc. Apparatus for determining the color characteristics of a gem
US4259011A (en) * 1979-11-05 1981-03-31 Crumm John C Optical gem analyzer
US4384769A (en) * 1981-05-08 1983-05-24 Jos. Schneider Optische Werke Aktiengesellschaft Illuminating system for test projector
US4569594A (en) * 1982-10-14 1986-02-11 Nestec S.A. Color value measurement
US5835200A (en) * 1990-04-24 1998-11-10 Gersan Establishment Method and apparatus for examining an object
DE19506192A1 (de) * 1995-02-23 1995-07-20 Christian Gassner Edelstein-Absorbtionsspektralphotometer
DE29517144U1 (de) * 1995-02-23 1996-01-11 Gassner, Christian, 63165 Mühlheim Edelstein-Absorbtionsspektralphotometer
US5835205A (en) * 1996-02-12 1998-11-10 C3, Inc. Optical testing system for distinguishing a silicon carbide gemstone from a diamond
USRE44963E1 (en) * 1997-01-10 2014-06-24 Diamond Technologies, Inc. System and method for computerized evaluation of gemstones
US6473164B1 (en) 2000-02-16 2002-10-29 Gemological Institute Of America, Inc. Systems, apparatuses and methods for diamond color measurement and analysis
US20060190292A1 (en) * 2000-10-12 2006-08-24 Gemological Institute Of America, Inc. Systems and methods for evaluating the appearance of a gemstone
US20070043587A1 (en) * 2000-10-12 2007-02-22 Reinitz Ilene M Systems and methods for evaluating the appearance of a gemstone
US20070067178A1 (en) * 2000-10-12 2007-03-22 Reinitz Ilene M Systems and methods for evaluating the appearance of a gemstone
US7834987B2 (en) 2000-10-12 2010-11-16 Gemological Institute Of America, Inc. Systems and methods for evaluating the appearance of a gemstone
WO2007069242A1 (en) * 2005-12-12 2007-06-21 Platform Development & Investment Ltd. Assessment of diamond color
US20090182520A1 (en) * 2005-12-12 2009-07-16 Yoav Luxembourg Assessment of diamond color
US20080140961A1 (en) * 2006-12-07 2008-06-12 Atherton William E Single channel memory mirror

Also Published As

Publication number Publication date
GB1316382A (en) 1973-05-09
JPS5423270B1 (xx) 1979-08-13
DE2011931A1 (xx) 1972-01-13
DE2011931B2 (de) 1972-01-13

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